Conveyor devices of the stated kind are used for different purposes and in different industries. For example, conveyor devices are used within a manufacturing line to convey workplaces from one processing station to another processing station. The conveyance path in a particular conveyor device in this activity is subdivided into partial paths, to which conveyance means are assigned, in order to convey a workplace in the conveyance direction along the partial path.
Conveyor devices of the stated kind are known from the state-of-the-art technology and first of ail feature primary conveyance means for workplace conveyance along a first partial path of the conveyance path. Furthermore, these conveyance devices feature secondary conveyance means for workpiece conveyance along a second partial path of the conveyance path. In this arrangement, the second partial path is positioned upstream, specifically immediately upstream, of the first partial path of the conveyance path in the conveyance direction, in order to feed workpieces to the first partial path. In this connection the expression “immediately upstream” is understood to mean that no additional partial path with conveyance means for workpiece conveyance is arranged between the first and second partial paths of the conveyance path.
However, the known conveyance devices of the stated kind present the inherent disadvantage that a deviation in the conveyance speeds of workpiece conveyance in the primary and secondary conveyance means will mean that either the geometric spacing between the workpieces in the conveyance direction becomes unreasonably large, or the workpieces may collide with each other and be damaged, especially in the transition region between first and second partial path. In this respect the known conveyance devices of the stated kind present the disadvantage of a lower workplace conveyance rate or the disadvantage of a high rejection rate for workpieces. The disadvantages mentioned result in loss of economical operation of a corresponding conveyance device.
One known solution to the problems is specified by the introduction of temporary storage for workpieces (buffer) to which workpieces are fed from the conveyance path if there is any danger that any spacing between workpieces lined up along the conveyance path will fall below the minimum, which could threaten collisions among them. The workpieces located in the workpiece temporary storage are fed to the conveyance path at a later time.
Furthermore, designs are known for more accurately synchronizing the partial paths with respect to their conveyance speed or combining them into one large conveyance path or to reduce the number of conveyance means.